(b) where the agreement or order is made before 1 May 1997, the day that is after 30 April 1997 and is the earliest ofi. the day specified as the commencement day by the payer and the recipient of the child support amount payable or receivable under the agreement or order, in a valid election made under subparagraph i of paragraph b of the definition of “commencement day” in subsection 4 of section 56.1 of the Income Tax Act (R.S.C. 1985, c. 1 (5th Suppl.)) after 19 December 2006 in relation to the agreement or order,
ii. where the agreement or order is varied after 30 April 1997 to change the child support amounts payable to the recipient, the day on which the first payment of the varied amount is required to be made,
iii. where a subsequent agreement or order is made after 30 April 1997, the effect of which is to change the total child support amounts payable to the recipient by the payer, the commencement day of the first such subsequent agreement or order, and
iv. the day specified in the agreement or order, or any variation of the agreement or order, as the commencement day for the purposes of this Part or, if the day is specified in such a variation made after 19 December 2006, of the Income Tax Act;